The present invention relates generally to a downhole rod pump assembly, and more particularly, but not by way of limitation, to such an assembly adapted for safe use in steamflood operations.
A typical downhole rod pump is seated in a seating nipple within a production tubing string, and the lower end of the production tubing string is always open to the well bore so that fluid from the well is drawn into the pump and then pumped from the pump upward through the production tubing string upon reciprocable motion of a string of sucker rods connected between the rod pump and a walking beam pump jack located at the ground surface.
A safety problem is encountered with typical prior art rod pump apparatus when such apparatus are used in a well producing high temperature fluids. For example, in some steamflood operations, the fluid from the well is at a temperature in a range from 90.degree. F. to 310.degree. F. when it reaches the ground surface.
If the rod pump fails, it is sometimes very difficult or impossible to pull the sucker rods and the rod pump out of the well because of the hot fluid flow, or the pulling unit crew may be subject to severe burns from the hot fluid if they do attempt to pull the sucker rods and the rod pump from the well.
Very often, such a well cannot be killed with high density drilling mud in order to allow the rods and pump to be pulled.
The present invention overcomes these problems by providing a production tubing extension extending below the seating nipple and having a spring loaded flapper valve on the lower end of the production tubing extension. The rod pump is provided with a dip tube having a sufficient length such that when the rod pump is seated in the seating nipple, the dip tube engages the flapper valve and holds the flapper valve open. A polished rod at the upper end of the sucker rod string is provided with an extended length so that the rod pump may be positioned at a sufficient distance above the seating nipple so that the dip tube is above the flapper valve allowing the flapper valve to close, while the polished rod is still sealed within a stuffing box connected to an upper end of the production tubing string.
It is, therefore, a general object of the present invention to provide an improved downhole rod pump assembly.
Another object of the present invention is the provision of a downhole rod pump assembly including a spring loaded flapper valve attached to a lower end of an extension of the production tubing.
Yet another object of the present invention is the provision of a downhole pump assembly having a flapper valve on the production tubing, a dip tube connected to a lower end of the rod pump for opening the flapper valve, and an extended length polished rod for allowing the polished rod to be sealed within a stuffing box when the dip tube is at a position above the flapper valve.
Still another object of the present invention is the provision of improved methods of installing and removing a rod pump from a well.
Other and further objects, features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the following disclosure when taken in conjunction with the accompanying drawings.